1. Field of the Invention
The present invention relates to the sealing of channel drainage systems, and more specifically to the sealing of high capacity channels typically referred to as wide channel drainage systems.
2. Description of Related Art
Robust drainage channels with a high hydraulic capacity are required for surface drainage in large areas such as distribution centres, car parks, airports and farm yards. The water carried in the drains from such surfaces will inevitably carry environmental pollutants such as hydrocarbons, pesticides, organic effluents and milk. It is therefore important to prevent such water from leaking out of the drain into the surrounding sub-soil where it may contaminate ground water supplies and produce other harmful environmental effects such as eutrophication. Natural stormwater leaking from the drainage system into surrounding contaminated land may also disturb and mobilise any latent toxins that may reside in the soil, particularly on brownfield site applications.
Polymer concrete U shaped channel drain sections are typically joined by being butted together end to end to form a channel. These joints are not water tight and the concrete haunch is relied upon to prevent leakage into the surrounding sub-soil. Escaping water may erode and therefore weaken the concrete. Where sealing is required sealing compounds are used.
Zurn Industries, Inc. in U.S. Pat. No. 6,000,881 describes a modular polymeric trench drain system in which the modules act as both former and liner. The Zurn modules define a U shaped channel section terminating in a restricted throat defining a slot drain at the surface. Zurn describes the technical problem of pressure from wet concrete against the trench drain walls causing deformation during installation. Flanges are formed at each end of the modules to facilitate joining of the sections. At one end the flange has a peripheral groove member to form a female section that mates with a male section on an adjacent flange of the next module section. In an alternative embodiment the flanges are omitted and a lip serves as a male section for engaging into a female section that is not illustrated
GB-A-2 373 530 (ACO Technologies plc) describes a wide channel drainage system in which plastics channel liner sections each defining a complete pipe section, are connected to form a continuous channel. In that specification it is taught to interlock the channels by means of male and female connection details at opposite ends. However since the sections have no significant structural strength and are lightweight, it has been found that an unacceptable deformation occurs at the weaker, male end of the channel section. This is due to the hydrostatic forces exerted by the wet concrete surrounding the channel section.
Although Zurn acknowledges the technical problem of channel section deformation, the only solution proposed is the provision of clips to allow reinforcing and support rods to be held in horizontal and vertical axes at either side of the sections. This leaves the ends vulnerable.